Encapsulation technologies have numerous applications in a variety of industries when it is desirable to isolate a particular material until required. Encapsulation makes possible, for example, the ability to mask unpleasant tastes, to protect substances such as unsaturated fats and oils from oxidation, to control the release of encapsulated material, to convert a liquid material into a free flowing powder, to control flow properties, and to separate reactive materials until a particular reaction is desired. The encapsulated material may be released by mechanical, physical or chemical processes such as increasing the pressure or shear, increasing the temperature, dissolving the capsule wall, or letting the internal phase diffuse through the capsule wall.
Simple coacervation is the phenomenon of phasing a soluble polymer, such as gelatin, out of solution in order to encapsulate dispersed oil globules or solid particles within a uniform, continuous coating. This coacervation can be achieved by controlling the pH, temperature or polymer concentration. A typical procedure is to add a solution of salt to a solution of gelating containing the dispersed oil globules, thereby reducing the solubility of the gelatin causing it to coacervate around the surfaces of suspended oil globules and eventually precipitate out of the solution. The microcapsules may then be separated and dried.
Complex coacervation is a controlled reaction between two oppositely charged polymers to form an insoluble polymeric complex that will precipitate from solution. The most common combinations are gelatin and one of one or more ionic polymers, such as gum arabic, pectin, and microbial polysaccharides (e.g. gellan gum). In food products, gelatin-gum arabic coacervates have been used to encapsulate flavors for inclusion in cake mixes, chewing gum, confectionary and other products.
Complex coacervation, however, requires complicated steps and a strict control of process parameters such as pH and temperature. Although gelatin is used for most of the complex coacervation procedures because it has good amphoteric properties as well as the ability to gel at temperatures above refrigeration, the structural network formed may not have sufficient structural integrity when high molecular weight ionic polysaccharides such as gum arabic, carboxymethyl cellulose, and synthetic ionic polymers are used. Conventional high molecular weight polymers or oligomers used in encapsulation procedures have a number of other disadvantages. Such polymers give very high viscosity suspensions even at low concentrations and therefore limit the concentration of polymer that can be used in the encapsulation process. This makes the process difficult to carry out in practice. The capsules prepared using high molecular weight polymers are easily broken because the membrane has insufficient strength. In addition, the processing usually takes a long time, up to about 20 to 24 hours or even longer and requires a strict control of the processing conditions.
It is therefore important to provide a method of encapsulation which provides higher quality capsules and a higher yield of capsules. Such a method should be simple to operate and economical.